Accumulation of selected macronutrients and carbohydrates in melon tissue cultures: association with pathways of in vitro dedifferentiation and differentiation (organogenesis, somatic embryogenesis)

Abstract We investigated the association between the accumulation of selected macronutrient ions and soluble carbohydrates and the in vitro developmental fate of cotyledonal explants from two melon ( Cucumis melo L.) cultivars. The accumulation of all macronutrients was very significantly affected by the pattern of ontogenic development, genotype and their interaction. In both cultivars, a lower NO 3 − accumulation was observed in callus tissues, compared to differentiated embryogenic or organogenic cultures, while direct adventitious organogenesis was associated with a considerable increase in PO 4 3− concentration. The accumulation of K + depended on culture development in the following order: callus induction > somatic embryogenesis > adventitious organogenesis. The highest Mg 2+ concentration was associated with somatic embryogenesis and the lowest Mg 2+ and Fe 3+ concentrations were associated with callus induction. When considering the developmental process-specific accumulation over both genotypes, callus induction was associated with increased Ca 2+ , and carbohydrate concentrations and adventitious organogenesis was associated with increased NH 4 + and NO 3 − concentrations. In vitro cultures from both cultivars accumulated more PO 4 3− and K + , but less Mg 2+ than donor plants. Embryogenic cultures from one cultivar (Bolero) accumulated two-fold more NH 4 + and more than 21-fold NO 3 − than donor plants. However, the observed macronutrient concentrations in both cultivars in vitro were considerably lower than in the original Murashige and Skoog basal medium formulation. Results are discussed in view of the possible metabolic pathways requiring the studied macronutrients, as well as improving medium formulations and culture protocols for the micropropagation of this commercially important species.